Visualization display units are used to visualize large format images of up to several dozen square meters in size. These visualization display units are often placed in very large areas such as, for example, stadiums, airport halls or conference halls, for the benefit of persons who are in these areas.
Currently, display images are visualized on a visualization display unit having N columns and M lines of visualization screens (each screen having Y columns and X lines) from source images formed by a matrix of YO columns and XO lines. A conventional method includes the following steps:
(a) each source image XO YO is divided into MN equal sub-matrix windows. If the ratios XO/M and/or YO/N are not whole numbers, the matrix window corresponding to the last column and/or the last line of the visualization display unit will be smaller than the other matrix windows. In other words, the visualization of the source image will be partial. PA1 (b) The lines and the columns of each matrix window are interpolated by repeating each column N times and each line M times. PA1 (c) Each of the interpolated matrix windows are delivered to the corresponding screen of the visualization display unit. PA1 (a) The Y1 columns and the X1 lines of each image window are sub-sampled to produce an intermediate image matrix of Y2 columns and X2 lines (X2 Y2 image elements) in accordance with a column coefficient of sub-sampling K.sub.C =Y2/Y1 and a line coefficient of sub-sampling K.sub.L =X2/X1. K.sub.C and K.sub.L are each, independently, one of the values 1, 1/2, 1/3, etc. Each line and each column of the intermediate image respectively replace one or more lines or columns of the image window, and each of the elements of the intermediate image are calculated as the arithmetic mean or the weighted mean of the corresponding image elements of the image window which is being replaced. PA1 (b) The formed intermediate images are stored at the rate C, in printing/reading memories. PA1 (c) The stored intermediate images are read in the same order as they were stored and at a rate C' equal to or different from the rate C. PA1 (d) The columns Y2 and lines X2 of each intermediate image are over-sampled to produce an output image having a matrix of Y3 columns and X3 lines. The over-sampling is performed in accordance with a coefficient of over-sampling of columns E.sub.C =Y3/Y2 and with a coefficient of over-sampling of lines E.sub.L =X3/X2, where E.sub.C and E.sub.L are each any value greater than or equal to 1. Each element of the output image X3 Y3 is calculated as a weighted mean on the basis of the corresponding neighboring elements of the columns or of the lines of the intermediate image being over-sampled. Each output image of X3 Y3 elements are registered into a matrix of X4 Y4 elements, where Y3 is less or equal to Y4 and X3 is less or equal to X4. PA1 (a) a sub-sampling unit receiving data, in a digital form, from the image windows X1 Y1 at a rate C, the sub-sampling unit including: PA1 (b) a transmission control unit for receiving the formed intermediate images X2 Y2 and for delivering them one after another to the two printing/reading memories, each memory receiving an image X2 Y2; PA1 (c) two printing/reading memories constructed by a memory segmented into two zones, the first being used for printing and the second being used for reading, the roles of the two zones being interchanged when the printing of each image is terminated; PA1 (d) a transmission commutator unit for reading, at a rate C', different or equal to C, the memories one after another in the same order as the transmission control unit at the over-sampling unit; and PA1 (e) an over-sampling unit receiving, at a rate C', intermediate images X2 Y2 one after another, the over-sampling unit comprising:
If M is greater than N, or if N is greater than M, the display image produced will respectively be elongated or broadened with respect to the source image. In order for the display image to completely occupy the visualization surface which has MX lines and NY columns, these lines and columns must respectively be multiples of XO and YO.
There are several limits and disadvantages of the abovedescribed conventional method. Enlargement of the source image, either in width or in height, must be presented as a whole number, because the interpolation coefficients of the lines and the columns ar whole numbers (repetition), and the display images produced are hazy, especially in case of very large enlargements (strobe effect).
There are methods of image processing that can avoid haziness of the produced image by using complicated interpolation functions. These methods are valid only for processing static images or weak resolution images, and cannot be applied on visualization display units having a matrix of screens.